Cacodyl, which has an intolerable garlicky odor and is used in the manufacture of cacodylic acid, a cotton herbicide, has a mass percentage composition of 22.88% C, 5.76% H, and 71.36% As and a molar mass of 209.96 g/mol. What is the molecular formula of cacodyl?

The molecular formula of cacodyl is C₄H₁₂As₂.

Explanation:

Let's assume we have 1 mol of cacodyl, in that case we'd have 209.96 g of cacodyl and the following masses of its components:

209.96 g * 22.88/100 = 48.04 g C 209.96 g * 5.76/100 = 12.09 g H 209.96 g * 71.36/100 = 149.83 g As

Now we convert those masses into moles:

48.04 g C : 12 g/mol = 4.00 mol C 12.09 g H : 1 g/mol = 12.09 mol H 149.83 g As : 74.92 g/mol = 2.00 mol As

Those amounts of moles represent the amount of each component in 1 mol of cacodyl, thus, the molecular formula of cacodyl is C₄H₁₂As₂.